HIV-1 p24 antigen and anti-HIV-1 p24 antibody are important markers of HIV-1 reproduction and immune response. [1, 2, 5, 6, 8, 9, 13, 16, 18, 20-22, 25-28]. An intimate relationship exists between the presence of HIV-1 p24 antigen and the level of anti-HIV-1 p24 antibody in sera of HIV-1-infected subjects. A decrease in the level of anti-HIV-1 p24 antibody usually coincides with the appearance and persistence of circulating HIV-1 p24 antigen. Therefore, both of these markers are of great value for evaluating HIV-1 infection and predicting the progression in HIV-1-infected subjects.
HIV-1 p24 antigen and anti-HIV-1 p24 antibody detection assays are available as enzyme-linked immunosorbant assay (ELISA) kits from many commercial sources [10]. The detection of HIV-1 p24 antigen and anti-HIV-1 p24 antibody by existing kits are carried out separately, either in separate kits (e.g., Abbott) or in separate wells (e.g., Dupont HIV-1 p24 Core Profile ELISA, and Coulter HIV-1 p24 Antigen Assay System). The problem with the detection of HIV-1 p24 antigen and anti-HIV-1 p24 antibody separately is that in sera of HIV-1-infected subjects HIV-1 p24 antigen and anti-HIV-1 p24 antibody are usually present simultaneously and their interaction plays a crucial role in permitting their determination.
The basis of the above assay systems [10, 12, 14] is that immobilized anti-HIV-1 p24 antibody captures HIV-1 p24 antigen (in the DuPont, Coulter, Organon kits) or immobilized HIV-1 p24 antigen captures anti-HIV-1 p24 antibody (in the Abbott kits). In some kits (e.g., DuPont, Coulter), anti-HIV-1 p24 antibody is detected in a competition assay by using a mixture of a subject's serum with HIV-1 p24 antigen in wells with immobilized anti-HIV-1 p24 antibody.